A famous zoo-keeper once said that animals in zoos are the ambassadors for their cousins in the wild, a characterization that is misleading for more than one reason. To begin with, an ambassadorship is a job that someone performs of her own volition and not because she was placed into a cage or a tank and conscripted to amuse the members of another species. The idea of an involuntary ambassadorship makes as much sense as any other form of so-called employment in which the "employee" didn't apply for the job, doesn't have the option to quit, and has no say whatsoever regarding the terms of her employment. The word for that kind of an arrangement is immediately recognizable when applied to humans. We call it "slavery".
If you are someone else's property, if that person's or institution's control over your life is absolute, and if they arrogate to themselves the right to take your life when it suits them, then in no sense of the word are you an "ambassador". You are merely chattel. "Ambassador" is not even a euphemism in this case; it amounts to nothing more than a sinister misnomer.
The status of zoo animals as slaves is exemplified by Marius, the healthy two year-old giraffe who, having been deemed "surplus" by the Copenhagen Zoo, was then shot in the head, dissected in the presence of children, and his body fed to lions. That's some ambassadorship, isn't it?
The second reason that animals in zoos are not "ambassadors" for their cousins in the wild is that the behavior of animals in their native habitats is vastly different from that of those living in tiny enclosures inside completely artificial environments. I've seen elephants on the plains of Africa and I've seen them in zoos and there is simply no comparison. The natural state of all animals is to be free and when deprived of their freedom, animals invariably change and seldom for the better.
Many proponents of zoos argue that notwithstanding the inevitable shortcomings of these institutions, they are nonetheless educational and on that point I find it impossible to disagree. Keeping animals in captivity for profit and amusement is certainly educational in the sense that it teaches the young and impressionable how much progress we have yet to make regarding the rights of our fellow creatures. But education of that sort constitutes no argument whatsoever in favor of keeping these institutions in existence.